The prior art is replete with numerous examples of fuel cells which are employed for various end uses. A fuel cell is an electrochemical device which reacts a fuel and an oxidant to produce electricity and a byproduct which is typically water. A typical fuel supply for a fuel cell is hydrogen, and the typical oxidant supplied to the fuel cell is oxygen (or more commonly ambient air). Other fuels and oxidants can be employed depending upon operational conditions. Various fuel cell designs have been proposed through the years including fuel cells in various stack-like arrangements. Yet further, fuel cells such as described in U.S. Pat. Nos. 6,030,718 and 6,468,682 have been commercially introduced and have avoided many of the shortcomings associated with stack-like designs and arrangements. The teachings of each of these patents are incorporated by reference herein.
In U.S. Pat. No. 6,096,449 to Fuglevand et al., the inventors disclosed a shunt controller which is electrically coupled with a fuel cell and which at times shunts electrical current between the anode and cathode of the fuel cell to achieve various benefits including boosting the electrical power output of same. It is speculated that this repeated, and periodic shorting causes each of the fuel cell membranes to be “conditioned”, that is, such shorting is believed to cause an increase in the amount of water that is made available to the membrane electrode diffusion assembly (MEDA) of the fuel cell thereby increasing that assembly's performance. Additionally, it is also conceivable that the shorting provides, at least in part, a short term increase in heat output that is sufficient to evaporate excess water from associated diffusion layers that are mounted on or made integral with the membrane electrode diffusion assembly.
In U.S. Pat. No. 6,620,538, and which is incorporated by reference herein, a fuel cell power system was described and which included circuitry which was configured to measure the equivalent series resistance (ESR) of the fuel cell in timed relation to the shorting as described in the earlier U.S. Pat. No. 6,096,449. This equivalent series resistance (ESR) was then employed to adjust the operation of the fuel cell in order to optimize the hydration, and other operational characteristics of the fuel cell.
While the assorted fuel cells and other methodology which has been described, above, have worked with a great deal of success, further research has been conducted in order to develop other measures which are still further more accurate indicators of the operational hydration of a functioning fuel cell.
Therefore, a method and apparatus for controlling a fuel cell which avoids the shortcomings attendant with the prior art devices and practices utilized heretofore is the subject matter of the present application.